ELECTROSTATIC CAPACITY MEASURING CIRCUITS FOR ELECTROSTATIC CAPACITY SENSOR HAVING PARASITIC CAPACITANCE

摘要

PURPOSE: A capacitance measurement circuit of a capacitance sensor with parasitic capacitance is provided to accurately measure capacitance without an error. CONSTITUTION: A capacitance measurement circuit comprises a sensing unit(110), a charge amplifying unit(120) and a compensation unit(130). The sensing unit comprises a capacitance sensor and outputs sensed capacitance and parasitic capacitance together. The compensation unit comprises a compensation capacitor and a reversal amplifier. The compensation unit outputs compensation capacitance corresponding to the parasitic capacitance. The charge amplifying unit converts the output signal of the sensing unit and the output signal of the compensation unit into electric signals. The charge amplifying unit amplifies and outputs the electric signals.